linux-kernel - Re: [PATCH v2 02/10] clk: imx95-blk-ctl: Save/restore registers when RPM routines are called

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Message-ID: <aHkY51MOgl4v2Y9/@lizhi-Precision-Tower-5810>
Date: Thu, 17 Jul 2025 11:38:15 -0400
From: Frank Li <Frank.li@....com>
To: Laurentiu Palcu <laurentiu.palcu@....nxp.com>
Cc: imx@...ts.linux.dev, Abel Vesa <abelvesa@...nel.org>,
	Peng Fan <peng.fan@....com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, dri-devel@...ts.freedesktop.org,
	linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 02/10] clk: imx95-blk-ctl: Save/restore registers when
 RPM routines are called

On Thu, Jul 17, 2025 at 03:23:38PM +0300, Laurentiu Palcu wrote:
> Hi Frank,
>
> On Wed, Jul 16, 2025 at 02:29:01PM -0400, Frank Li wrote:
> > On Wed, Jul 16, 2025 at 11:15:06AM +0300, Laurentiu Palcu wrote:
> > > If runtime PM is used for the clock providers and they're part of a
> > > power domain, then the power domain supply will be cut off when runtime
> > > suspended. That means all BLK CTL registers belonging to that power
> > > domain will be reset. Save the registers, then, before entering suspend
> > > and restore them in resume.
> > >
> > > Also, fix the suspend/resume routines and make sure we disable/enable
> > > the clock correctly.
> > >
> > > Signed-off-by: Laurentiu Palcu <laurentiu.palcu@....nxp.com>
> > > ---
> > >  drivers/clk/imx/clk-imx95-blk-ctl.c | 25 +++++++++++++------------
> > >  1 file changed, 13 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/drivers/clk/imx/clk-imx95-blk-ctl.c b/drivers/clk/imx/clk-imx95-blk-ctl.c
> > > index c72debaf3a60b..3f6bcc33bbe99 100644
> > > --- a/drivers/clk/imx/clk-imx95-blk-ctl.c
> > > +++ b/drivers/clk/imx/clk-imx95-blk-ctl.c
> > > @@ -453,7 +453,9 @@ static int imx95_bc_runtime_suspend(struct device *dev)
> > >  {
> > >  	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
> > >
> > > +	bc->clk_reg_restore = readl(bc->base + bc->pdata->clk_reg_offset);
> > >  	clk_disable_unprepare(bc->clk_apb);
> > > +
> > >  	return 0;
> > >  }
> > >
> > > @@ -461,7 +463,10 @@ static int imx95_bc_runtime_resume(struct device *dev)
> > >  {
> > >  	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
> > >
> > > -	return clk_prepare_enable(bc->clk_apb);
> > > +	clk_prepare_enable(bc->clk_apb);
> >
> > Need check clk_prepare_enable()'s return value!
> >
> > > +	writel(bc->clk_reg_restore, bc->base + bc->pdata->clk_reg_offset);
> > > +
> > > +	return 0;
> > >  }
> > >  #endif
> > >
> > > @@ -469,17 +474,12 @@ static int imx95_bc_runtime_resume(struct device *dev)
> > >  static int imx95_bc_suspend(struct device *dev)
> > >  {
> > >  	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
> > > -	int ret;
> > >
> > > -	if (bc->pdata->rpm_enabled) {
> > > -		ret = pm_runtime_get_sync(bc->dev);
> > > -		if (ret < 0) {
> > > -			pm_runtime_put_noidle(bc->dev);
> > > -			return ret;
> > > -		}
> > > -	}
> > > +	if (pm_runtime_suspended(dev))
> > > +		return 0;
> > >
> > >  	bc->clk_reg_restore = readl(bc->base + bc->pdata->clk_reg_offset);
> > > +	clk_disable_unprepare(bc->clk_apb);
> > >
> > >  	return 0;
> > >  }
> > > @@ -488,10 +488,11 @@ static int imx95_bc_resume(struct device *dev)
> > >  {
> > >  	struct imx95_blk_ctl *bc = dev_get_drvdata(dev);
> > >
> > > -	writel(bc->clk_reg_restore, bc->base + bc->pdata->clk_reg_offset);
> > > +	if (pm_runtime_suspended(dev))
> > > +		return 0;
> > >
> > > -	if (bc->pdata->rpm_enabled)
> > > -		pm_runtime_put(bc->dev);
> > > +	clk_prepare_enable(bc->clk_apb);
> > > +	writel(bc->clk_reg_restore, bc->base + bc->pdata->clk_reg_offset);
> > >
> > >  	return 0;
> > >  }
> >
> > Look like needn't imx95_bc_resume() and imx95_bc_suspend()
> >
> > DEFINE_RUNTIME_DEV_PM_OPS() will use pm_runtime_force_suspend(), which
> > do similar things with above logic.
>
> As I said for v1, we cannot use DEFINE_RUNTIME_DEV_PM_OPS(). This driver
> is used for various clock providers and RPM can be disabled for some of
> them (see rpm_enabled flag in platform data). When RPM is disabled and
> DEFINE_RUNTIME_DEV_PM_OPS() is used, pm_runtime_force_suspend() is
> called, as you pointed out, and suspend() is never called.

Sorry, I missed your message at v1. do you know which flag impact this?

Frank

>
> Thanks,
> Laurentiu
>
> >
> > Frank
> >
> >
> > > --
> > > 2.34.1
> > >